The pecan, which is a large deciduous tree (Carya illinoinensis) is a species of hickory native to Mexico and the south-central and southeastern regions of the United States. A pecan, like the fruit of all other members of the hickory genus, is not truly a nut, but is technically a drupe, a fruit with a single stone or pit, surrounded by a husk. The husks are produced from the exocarp tissue of the flower, while the part known as the nut develops from the endocarp and contains the seed. The husk itself is aeneous, oval to oblong, 2.6-6 cm long and 1.5-3 cm broad. The outer husk is 3-4 mm thick, starts out green and turns brown at maturity, at which time it splits off in four sections to release the thin-shelled nut.
Today, the U.S. produces between 75% and 85% of the world's pecans, with an annual crop of 180-240 thousand metric tons, in-shell basis, from more than 10 million trees. Historically, the leading pecan-producing state in the U.S. has been Georgia, followed by Texas, New Mexico, Arizona, Louisiana, and Oklahoma. Pecans are also grown in Alabama, Florida, Arkansas, Kansas, Missouri, South Carolina, and Hawaii. Outside the United States, pecans are grown in Australia, Brazil, China, Israel, Mexico, Peru, and South Africa.
The seeds (nuts) of the pecan are edible, with a rich, buttery flavor. They can be eaten fresh, dried, roasted or used in cooking, particularly in sweet desserts. One of the most common desserts with the pecan as a central ingredient is the pecan pie, a traditional Southern U.S. dish. Pecans are also a major ingredient in praline candy.
The pecan nut meat is dicotyledonous, having two halves. An unbroken nut meat is classified by the USDA (United States Department of Agriculture), as a separated half, which has not been significantly damaged. (To qualify as a half kernel, the kernel may not have more than one eighth of the kernel missing, inclusive of the joiner piece between the two halves.)
Cracking and shelling pecans and removing the edible nut meat with minimal breakage is the ultimate aim of all pecan nut processing operations. Modern mechanical shelling operations typically recover between 50%-75% unbroken nut meats. Many shelling operations in Mexico have resorted to shelling by hand in order to achieve a higher percentage of unbroken nut meats. The difference in price received between unbroken and broken nut meats is substantial and the additional indirect losses incurred from breakage include, amongst others, loss of small pieces and nut meat dust to waste, additional labour cost in sorting pieces, a higher degradation and potential for development of rancidity factor in pieces and a higher percentage contamination of pieces with shell.